Fuse



Jan. 24, i950 p, H THOMPSQN 2,495,431

FUSE

Filed May 27, 1944 FIG. I. 78 f fx 33 4 /5 9 75 7 ff \A XM l 1 FG-2. 5se@ 55 65 57 Patented Jan. 24S, 1950 FUSE Parke H. Thompson, Kirkwood,Mo., assignerto Amp Corporation, St. Louis, Mo., a corporation ofMissouri Application May 27, 1944, Serial No. 537,563

1 Qiaim. 1

This invention relates to fuzes, and with regard to certain morespecific features, to pointdetonating fuzes for projectiles and thelike.

Among the several objects of the invention may be noted the provision ofa completely safe, simple, compact and permanently reliablepointdetonating fuze for projectiles and the like;l the provision of afuze of this class which, when attached to a shell, provides anair-tight seal to prevent breathing of atmosphere into and out of theprojectile so as to avoid deterioration of its contents; and theprovision of a fuZe of this class which is easy to manufacture. Otherobjects will be in part obvious and inA part pointed out hereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts which willbe exemplified in the structures hereinafter described, and the scope ofthe application of which will be indicated in the following claim.

In the accompanying drawings, in which is `illustrated one of variouspossible embodiments of the invention,

Fig. 1 is a longitudinal section of the new vfuze, showing it in theunarmed or safe condition of its parts;

Fig. 2 is a. fragmentary view similar to Fig. 1 showing the parts inarmed condition;

Fig. 3 is a vertical section taken on line 3-3 of Fig. 1;

Fig. 4 is a vertical sectiontaken online 4--4 of Fig. 1; and,

Fig. 5 is a fragmentary detail of certain parts of Fig. 1 prior tocomplete assembly.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.

The invention is an improvement upon the construction shown in ScelzoUnited States Patent 2,155,100, dated April 18, 1939. It is applicableto `various classes of ammunition, for both smalland large calibers.However, it has particular advantages in connection with the smaller andm'edium sizes because of the small space within which the elements ofthe invention may be housed.

Referring now more particularly to Fig. 1, there isshown at numeral iatapered fuze body having la hollow threaded shank 3 for application tothe threaded end of a shell 5 shown in dot-dash lines. The shell has aninternally threaded front end Y,surrounded Aby Va front end seat and asusual carries the main explosive charge to be detonated by the fuzeperse. The shank 3 is formed in- .teriorly as a hollow cylinder I forreceiving a cylindric pre-consolidated pellet of booster charge materiali3. This material is held in place by means of a so-called Welsh plug 9pressed into undercut peripheral recess Il.

Since the manner of applying the plug 9 is of some importance, thedetails of this will be explained, referring to Fig. 5. This plug isinitially bulged as shown Fig. 5, with a cylindric margin which willallow it to be snugly inserted into the narrowest portion of an undercutgroove I l. This is done after the pre-consolidated booster chargepellet il? has been slipped vinto the cylinder 1. This pellet is aboutequal to or if necessary slightly longer than the cylinder 'l measuredout to the base of the groove ll. Thereafter, the plug S is pressed fromthe bulged condition shown in Fig. 5 tothe :dat condition shown inFig. 1. This eX- pands its margin to interlock in the undercut groove l.At the same time its central portion exerts a final rie-consolidatingelfect upon the booster charge i3, thus assuring that the latter willentirely compactly lill up the space in the cylinder T. This assuresreliable travel through the pellet I3 of the detonating wave which is toset it olf. Unreliable booster charge action is often due to itsimproper consolidation in its containing chamber, and this method ofre-consolidating it by means of the holding plug 9 increases itsreliability.

Extending forward from the cylinder 'I on the center line of the body Iis a cylindric connecting passage I5. At the rear end of this passage isa crimping groove l? for receiving a flange I9 of a primer cup 2l closedat its opposite end as shown at 23. This is sometimes known as a leadingcup, being filled with an explosive such as tetryl.

Beyond the passage l5, the body i is provided with a counterbore 25.This counterbore 25 connects with the passage l5 by means of a sphericalseat 27. The largest diameter of the seat 2l' is preferably smaller thanthe diameter of the counterbore 25 for reasons which will appear.

Extending at an angle from one side of the oounterbore 25 is a passage29 for accommodating an angularly located cantilever wire spring 3lwhich is staked into the bottom of the passage as indicated at 33.Obviously, other methods for fastening the spring may be employed. Thecross section of the passage 2S is optional but a round bore is shown.The counterbore 25 also includes at its outer endk a keyway 35 for a key3l'. Key 3l also seats in a keyway il in a. nose 39. Other equivalentkey means may be used.

Adjacent to, and connecting with the hole 29 in body l, the nose 39 isprovided with a radial recess 43 accommodating movement of the end ofspring 3|, as may be seen by comparing Figs. 1 and 2. The nose 39 has acentral passage or bore 45 communicating with the recess 43. The end 65of spring 3| normally extends into this passage 45.

At the forward end of the opening 45 is a counterbore 41. At itsrearward end the opening is ared out by means of a beveled portion 49.This beveled portion 49 is carried in an extending portion 5| of thenose, determined by a seat 52. Portion 5| telescopes into the counterfbore 25 of the body No threads are used at this point. A press t may beused. The diameter oi' the counterbore 25 and the position of thechamfer 49 are such as just to accommodate a spherical rotor 53 whichengages the spherical seat 21. This rotor is rotary in the spacelprovided for it.

The rotor is bored out along an axis of symmetry A-S which passesthrough its geometric center. This bore consists in a small-diameterportion 55 and -a larger counterbore 51. At the large end of thecounterbore 51 is a cross slot 59 which is symmetrical with respect tosaid axis A-S. This slot is designed to accommodate the spring 3| andallow it free movement. The counterbore 51 from the end of the bore 55to the slot 59 is filled with a sensitive detonating charge 11.

The normal position of spring 3| is such as suggested in Fig. 1, thatis, the rotor 53 is maintained with the axis of symmetry A-S at anangle, `with respect to the center line of the fuze, which is greaterthan 45, preferably of the order ol or so. The exact value of this angleis not critical but it is important that it be over 45 or so, in orderthat in its safe condition the outlet 55 of the counterbore 51 may bepresented to the counterbore 25 on the outside of the spherical seat 21.The purpose of this will appear. The bias of the spring is inward towardthe center line of the fuze so that it tends to seat the rotor on itsseat 21, or at least prevents it from moving about in the space providedfor it.

In the bore 45 of the nose 39 is a hollow ring pin 6| which may be openat the front as indicated at 63 and closed at the rear as indicated at64. The point 61 of this pin extends from the enclosure 54. On theperiphery of the enclosure 64 and around the point 61 is an inwardlytapered skirt 69, which when the firing pin is back (Fig. l), takes up aposition outside of the spring end 65. This, under certain conditions tobe described forms an interlock for resisting radial movement of thespring. When the ring pin is forward, this interlocking action does notoccur (Fig. 2).

The outer surfaces of the body I and the nose 39 are machined on a taperwhich may be constant as shown, or otherwise. Closely tting over thetaper is a tapered cover or shield cup 1I having a truncated, closed top13 forming a drum over the open end of the counterbore 41. The area ofthe inside of the drum 13 is several times larger than the projectedarea of the firing pin 6I considered as a piston in bore 45.

At its base, the cover 1| is spun over as indicated at 15 in Fig. 5.This is done after its application to the assembled nose 39 and body Itis not spun completely at against the undercut bottom or shoulder seat18 of the body but is left slightly angular as shown in Fig. 5. Hencewhen the fuze assembly is screwed to the shell 5,

lll

the ange 15 is springingly deformed so as to assure a perfect hermeticseal against entry into the mechanism of foreign elements. This sealprevents breathing of the atmosphere into and out of the mechanism withtemperature changes. Thus fuzes made according to the invention may bestored for much longer periods of time without deterioration of theircontents.

An additional function of the cover 1| is to provide means for properlydrawing the cover against the nose 39 to the body without employment ofthreads of any kind. The initial position of the spun ilange 15 isangular as indicated in Fig. l5. Thus when the threaded attachment ismade between the body and the shell 5, the resulting deformation of theange 15 has a fulcrum effect which draws back the conical cover as awhole, thus firmly drawing it down on the nose 39 and the body I. Sincethe nose and the body i form a continuous rearwardly flaring conical ortapered surface engaged throughout by the corresponding inner surface ofthe cover 1|, the nose is wedgingly held by the cover even though thetelescoping t between the nose and body be other than the press-fitvariety. Thus a permanently proper relationship between the nose andcover is assured despite any variations in the said telescopic t. Also,since the entire conical surface of the cover is supported by the solidbody and nose damage from accidental blows is avoided. 1t is to beunderstood that the term tapered as used herein includes conical andogive forms. It will be noted that the only threads employed in thewhole construction are those for attaching the fuze as a whole to theshell 5, those which would ordinarily be used bet/Ween the nose and thebody having been eliminated.

Operation is as follows:

Regardless of the position of the ring pin 6|, the normal bias of thespring 3| is to the inward position shown in Fig. 1. It thereforecooperates with the groove or notch 59 and holds the rotor 53 in thestated approximate 70 position of the axis A-S. Forces due to normalhandling of the ammunition are normally not capable of deflecting thespring 3| enough to permit the rotor 53 to move more than a Small amountfrom this position. Furthermore, any temporary displacement of thespring 3| under almost inconceivable conditions of handling would befollowed by prompt return to the holding position shown in Fig. 1,Without imposition on the rotor of any forces which might send it to thearmed position.

The normal bias of the spring 3| tends to main- -tain the rotor 53 onthe spherical seat 21, thus sealing off the passage I5 from thedetonating charge 11. Furthermore, the angle of the axis A-S is suchthat the opening 55 from the detonating charge is directed into thecounterbore 25 and not against the seat 2,1. Hence if an over-sensitivedetonating charge should accidentally explode of its own accord, itsexpansive force would not be directed against the leading cup 2| inpassage |5. This preserves the booster charge I3 against detonation. Theexpansive force is then safely expended in the passages 25 and 45. Thisimportant safety feature is due to the high angle of the axis A-S whichkeeps the passage 55 forward with respect to the seat 21. This highangle has another advantage which will be explained at the proper pointherein.

In view of the above, it is clear that the fuze is statically safe.

Next, assume that the shell is loaded into a gun barrel and red by thepropellent charge (not shown). Both linear and angular acceleration thenset in as the Shell passes through the barrel. This at rst involvesinitial linear set-back forces on all movable members.

Thus a set-back force is operative upon the rotor 53 which tends to seatit firmly upon the spherical seat 2l. The charge Vi is positionedsymmetrically with respect to the center line C-L; also the bore 55 andgroove 59 represent losses of metal from the rotor having aboutequalmoments with respect to this center line C-L so that, in view of thefriction on said seat 21, the rotor maintains its safe position underlinear acceleration along line C-L (Fig. 1).

It will also be noted that a set-back force is operative upon the spring3| and since it is anchored at 33 farther from the center line C-L thanits free end 65, a counterclockwise moment is applied to the spring.This adds to the normal bias of the spring in helping to maintain therotor 53 seated on the spherical seat 2. The setb ack force on ring pin6i adds to this counterclockwise moment on spring 3| by pressingbackward on the spring end 65. Thus the fuze is bore safe, for, shouldthe detonator Il for some unknown reason at this time explode, thepressure at seat 2l' would positively block transmission of thedetonation to the booster charge i3.

The linear acceleration which causes a setback force on the ring pin 6|also holds it back so that the flange 69 locks around the end of thespring 3|. Therefore as angular acceleration occurs, due to the ridingof the gun, the flange 65 acts as an interlock preventing thecentrifugal action of spring 3| from substantially moving it outward.Therefore, as long as linear acceleration continues, which is as long asthe shell is in the gun barrel, the rotor positively remans in its safeposition, as indicated in Fig. 1.

The relationship between parts continues in the Fig. l position untilthe shell leaves the gun barrel. At this time linear acceleration ceasesand linear deceleration sets in, due to frictional forces exerted uponthe projectile in passing through the air. Since these forces are notapplied to the floating ring pin 6|, it drifts forward toward drum 13.It should be noticed, however, that the frictional forces on the shellexert a much smaller component toward effecting angular decelerationthan they do toward effecting linear deceleration. Therefore, althoughthere is enough linear deceleration to cause the pin 6| to driftforward, as indicated in Fig. 2, the angular velocity continues highenough so that the centrifugal force bends the spring 3| out radiallyfrom the slot 59. Since the density of the detonating charge 'l1 in thepassage 51 is less than the density of the rotor 53, which is made, forexample of commercial brass, and since A-S is an axis of symmetrybetween two centroids not in the same plane normal to C--L, this axisA--S will tend to swing into coincidence with the center line C-L of thefuze assembly. In this position the centroids are co-planar. This placesthe passage 55 in communication with passage 5 as indicated in Fig. 2,the rotor remaining stable under rotation in the Fig. 2 position. Theprojectile is then armed in flight. It appears from tests that thearming in flight is desirably delayed until an initial short part of thetrajectory has been traversed. There are several possible explanationsfor this, one being that as the spring 3| releases the rotor, the latterbecomes in effect a gyroscopic element free to precess the axis A-Stoward axis C--L. The time required by gyroscopic precession involvesthe desired delay, particularly in view of the high initial anglebetween A-S and C-L. Toward the end of the precession, there occurspossibly also a conical nutation' of A-S with respect to C-L which makesthe opening 55 nutate in a circle around the opening l5 without havingthese openings connect until the very last stages of the movement of theaxis A-S. This nutation is possible because the spring 3| at this timeis disconnected. It is of course also possible that the last part of themotion may involve a period of damped oscillations of the opening 55across the opening l5. In any event, the initial large angle of A-S withrespect to C--L seems to introduce a very desirable safe period duringthe initial traverse of the trajectory.

After the device is once armed in ight, as shown in Fig. 2, should theangular velocity drop to a point allowing the spring 3| to press againstthe' armed 'rotor 53, the device would remain armed since the springwould simply hold the rotor in the armed position. Thus once armed, thefuze is permanently armed while in ilight.

Rain drops encountered by the drum I3 will not deform it and withoutdeformation the drum 13 is incapable of driving the ring pin 9| backwardl Therefore premature detonation will not occur during flight in badweather.

When the shell reaches its objective, collision with the fuze deformsthe drum 13 which causes a pressure wave from drum '13 to impingeagainst the 'firing pin 6|. The projected area of the piston-like ringpin 6|, being substantially less than the area of the inside of the drum'i3 (for example in the ratio of 1:4), any pneumatic compression drivesthe firing pin at a velocity higher than the deflection rate of thedrum. vThus the action of the firing pin in moving backward upon impactis very fast, driving its point 61 into the detonating charge which resagainst the cup 2|. Thissets off the booster charge I3 against themember 9. It is to be understood that the cup 2| may be dispensed withand the detonating charge permitted to re directly down the channel I5into the booster charge.

Certain advantages of the angle greater than 45 specied for the axis ofsymmetry A-S have already been stated. An additional one is that theeffective centrifugal moment, at a given angular velocity of the shell,tending to turn the rotor from the Fig. l to the Fig. 2 position ismaximum at 45 of AS. Hence it is less at angles greater than 45 whilethe spring is latohed in the rotor notch. This reduces the static camaction of the bottom of the notch 59 on spring 3| under acceleratingconditions in the gun barrel, since the position of rotor axis A--Sduring acceleration is greater than 45. This increases bore safety.

Another important feature of the invention is that the forms of theparts 39 and 6| lend themselves to easy manufacture by die casting. Nothreads are involved, except those at 3 necessary to attach the entirefuze to the shell. The integral protective cover 'li may easily bepressed or spun. Assembly is simple and fool-proof.

Unlike the Scelzo construction above mentioned, the present fuze doesnot depend merely upon friction between the rotor 53 and its seat 21 fordelaying or preventing arming in the gun barrel. It has a positiveinterlock in the spring 3| and notch 59 held by the pin 6| whichpositively prevents arming in the barrel. In this respect spring 3| andnotch 59 may be designated asA a latch. In addition, this latchinterlock acts amanti as a .positive driving `connection between thebody l and the rotor '53 so that 'the latter is positively angularlyaccelerated'at the same rate as the angular acceleration of the body. Amere 'fric'- is released by drift of the `pin or striker 6I.

The delayed arming means is claimed vin lmy copending application,Serial No. 646,530, filed February 9, 1946, for FuZe, a division of thisapplication, and to which this reference is made under rule 43. V

yIn view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes `could be made in the above constructions Withoutdeparting yfrom the scope of the invention, it is intended that allmatter contained in the above description or shown in thev accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

A fuze for a shell, the latter having an internally threaded iront endsurrounded by a iront end seat, said iuze comprising a body includingthreads for attachment to the threaded shell, said body having arearwardly directed seat facing said front end seat upon threading, anose, said body having a forward recess for telescopic reception of arearward extension from said nose, the outsides of the body and nosebeing formed as a continuous forwardly tapered surface, a one'- f pieceforwardly tapered sheet metal hollow shield cup, the inside of which isadapted to contact substantially throughout said tapered surfaces of thebody and nose, and an inwardly directed flange on said shield cupfulcrumed to bias the shield cup back upon the body vand nose when theshell and body are threaded together so as permanently to hold thesetogether regardless of the character of the telescopic nt and wherebythe contents of the .fuz'e are hermetically sealed.

PARKE` H. THOMPSON.

REFERENCES CITED UNITED STATES PATENTS Number Name v Date 911,420Maunsell Feb. 2, 1909 1,311,081 Martin July 22, 1919 1,316,607 WatsonSept. 23, 1919 1,342,652 Sullivan June 8, 1920 1,503,632 Brayton Y Aug.5, 1924 1,532,341 yPearson Apr. 7, 1925 2,085,053 Teitscheid June 29,1937 2,128,838 Methlin Aug. 30, 1938 2,428,380 f Nichols Oct. 7, 1947FOREIGN PATENTS Number Country Date 13,901 Great Britain v June 20, 1904129,041 Great Britain July 10, 1919 y'507,795 France July 5, 19207955830 France Jan. 13, 1936

